1. Field of the Invention
The present invention relates to a flat panel display (FPD) in which a drive integrated circuit (IC) chip is mounted onto a display panel by a chip-on-glass (COG) method. The present invention also relates to a drive IC chip for a flat panel display.
2. Description of the Related Art
For small size and low power consumption, flat panel display devices such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), ELD (Electroluminescent Display), and VFD (Vacuum Fluorescent Display) have been introduced. In these flat panel display devices, the LCD has been most widely adopted nowadays because of good picture quality and low power consumption. Although portable televisions and notebook computers having the LCD have been marketed, there are various problems yet to be solved.
In an LCD, packaging techniques for connecting a drive IC chip, which provides a drive signal to the LCD panel, include wire bonding (WB), tape automated bonding (TAB) and chip-on-glass (COG) methods. In these packaging techniques, the chip-on-glass (COG) method has been most actively researched recently because it can increase the density of the liquid crystal display element and minimize external size of the LCD in spite of various disadvantages.
However, when a plurality of integrated circuit chips are mounted on one surface of a glass substrate, a wide area is required to wire the bus lines for transmitting the common signals such as power supply and data signal between the chips. This greatly reduces the available area of the surface of the glass substrate. Typically, the bus lines are formed from the conductive layers such as ITO (Indium Tin Oxide) layer on the substrate thereby significantly increasing the resistance of the bus lines.
U.S. Pat. No. 5,402,255, issued on Apr. 3, 1995 to Nakanishi et al., discloses a device utilizing the internal circuits of drive IC chips to transmit the common signals between the chips. Referring to FIG. 1, Nakanishi et al. disclose a drive chip 100 having output terminals 110 for providing drive signals to an LCD panel. The left-hand and right-hand terminals 120 and 130 for input and output signals are connected to each other through an internal circuit 140 of the chip 100. Typically, the internal circuit of IC chip is made of aluminum alloy. Although aluminum alloy has higher electrical conductivity as compared with ITO, the problems of signal distortion or voltage (or IR) drop are still observed. Furthermore, when extra metal traces are built into the architecture of a chip, the manufacturing process of wafer becomes complicated thereby increasing the production cost.